Packaging of the aforementioned type which contain a certain number of containers such as, for example, bottles (for water or other beverages), cans (for beer or other beverages or conserves), paper or cardboard containers (for milk, sugar, rice, pasta and similar products) are well known. These containers are arranged alongside one another in an ordered manner, in a certain number of lines and rows (the terms "lines" and "rows" obviously being interchangeable) and then wrapped in a sheet of plastic obtained from a film in the form of a continuous strip wound up in reels, so as to obtain a packaging which has an overall parallelepiped shape. The packaging may enclose a minimum of two products, while the maximum number thereof will in practice depend on the overall dimensions and weight of the packaging. In the case of bottles of water for example, said bottles are usually sold to the public in the form of packs of six bottles ordered in an arrangement of two lines and three rows, so that each pack contains three pairs of bottles arranged side by side. However, it may happen that a purchaser wishes to buy a certain number of bottles less than the number contained in the pack (for example only one pair of bottles). In order to do so, the purchaser is obliged to break the plastic film with his/her hands, which is not only difficult, but also normally upsets the correct arrangement of the remaining bottles inside the packaging. Similarly, after having acquired the whole packaging, if one wishes to remove from it a bottle, one is again obliged to break the plastic film with the result that the remaining bottles, or at least some of them, are no longer retained in position and therefore no longer form a firm packaging.
It is known of a packaging for bottles having pre-cut lines (i.e. lines along which it is possible to easily perform breakage of the plastic film using one's hands) which are of limited length and formed in the plastic film and which affect, however, only part of the top side of the packaging along respective planes lying between two adjacent rows of bottles. This solution, however, does not overcome the drawbacks mentioned above since the removal of one bottle or a pair of bottles from the packaging remains a somewhat difficult operation and still involves free breakage of the part of the plastic film which is not pre-cut, resulting in the possibility that all or some of the other bottles inside the packaging may be freed.
The method for obtaining this packaging having the limited pre-cut lines described above consists substantially in wrapping in a conventional manner the set of six bottles to be packaged, using a section of plastic film of suitable length, normally polyethylene of the heat-shrinkable type, the section of film surrounding entirely the top and bottom surfaces and the two side surfaces (those comprised of three bottles). The assembly thus obtained is then placed in a conventional oven of the type used for causing shrinkage of the film following heating thereof, thus resulting in a conventional packaging. At this point, the relevant limited pre-cut lines are formed only on the top surface of the packaging, forming in the plastic film a respective series of suitably positioned incisions. As already mentioned, these limited pre-cut lines are formed over only a part of the width of the top surface of the packaging.
It is also known from European Patent Application EP-A-0717712 of a packaging for bottles in which pre-cut lines are formed along the entire perimeter of the packaging and lie in parallel vertical planes positioned between the various pairs of bottles.
The most economical method for achieving this result consists in providing beforehand in the plastic film intended to form the packaging for bottles a series of longitudinal and parallel pre-cut lines so that, when the film is cut into sections of suitable length for forming the packaging for the bottles, a continuous pre-cut line is formed between adjacent pairs of bottles. In this way removal of a pair of bottles is substantially facilitated, while the remaining bottles remain correctly packaged.
It has been noted, however, that such a solution, which theoretically appears to be the best solution for the problem, in practice has a serious drawback due to the fact that, in order to form the packaging, the section of plastic film which surrounds the bottles must be overlapped over a distance more or less equal to the width of the base of the packaging, so as to be able to carry out heat-sealing of the two overlapping flaps of the section of film. However, the machines which perform this operation are not currently able to ensure that overlapping of two end flaps of the section of plastic film is performed so as to overlap precisely the corresponding end of each pre-cut line, which in fact normally turn out to be offset (by even more than 1 cm) with respect to one another. This means that, when one wishes to separate a pair of bottles from the packaging thus obtained, the film at the bottom of the packaging still breaks in an irregular manner, since the breakage in the zone underneath the bottles, where overlapping of the film is performed, does not follow the pre-cut lines, with the result that the remaining bottles may not be retained as a firm packaging.